Autofocus problem with XH A1? at DVinfo.net

Etienne Didelot-Pothier · January 22nd, 2010, 02:02 AM

Hey there.

Anyone experiencing strange behaviour with instant AF?

In a normal situation (0db, 1/60, F3.2, 60i) with talents in front of a wall (either a bit dark or underexposed), the lens starts flickering and it has problem finding the right point to focus. I can't work with manual focus on that kind of job, because it's not predictable and really "on the go".

I'm not too happy with Canon's autofocus system (had same problem with GL2).

John Estcourt · January 23rd, 2010, 01:06 AM

Hi, having moved across from a sony camera I found the auto focus on the Canon to be slightly less responsive, however Auto focus should never really be trusted and the only way is to go manual.
If you really cant go manual then zoom in tight on the subject, press the instant auto focus then release prior to re framing and that way you will know the subject is in focus.
Hope this helps.
john

Chris Soucy · January 23rd, 2010, 01:56 AM

There is no "strange behaviour" with the Canon auto focus, it's as good as the camerman behind it.

Autofocus can only work if it has a discernible (to it) target to focus on.

A small forground target with an immense background target makes for a poor autofocus scenario, especially if the former has no real contrast or outline.

Dive into the menu's on the A1 and set grids to "ON":

[Display Setup] - [Markers] - [Grid]

If your target doesn't almost completely fill the box of the centre grid, IT WILL NOT FOCUS ON IT.

Throw in bad contrast, poor lighting and a possibly dirty IAF sensor and you have a dogs dinner, where it will "do it's own thing" despite what you may think it should be doing.

Do some tests and check it out and see for yourself how much of that centre box is required before the AF will consistantly lock to it, you'll be suprised (and no, it isn't any worse and actually a lot better than any other make of camera either).

It's a poor workman who blames his tools for a bad job.

CS

January 22nd, 2010, 02:02 AM	#1
Etienne Didelot-Pothier Regular Crew Join Date: Nov 2009 Location: Montreal, Quebec Posts: 59	Autofocus problem with XH A1? Hey there. Anyone experiencing strange behaviour with instant AF? In a normal situation (0db, 1/60, F3.2, 60i) with talents in front of a wall (either a bit dark or underexposed), the lens starts flickering and it has problem finding the right point to focus. I can't work with manual focus on that kind of job, because it's not predictable and really "on the go". I'm not too happy with Canon's autofocus system (had same problem with GL2). __________________ http://www.EDPimagerie.com Canon XH A1 - Rode NTG-2 - Canon 7D - 8" HD - 50mm f1.4 - 11-16mm f2.8 - 70-200 f4L

January 23rd, 2010, 01:06 AM	#2
John Estcourt Major Player Join Date: Oct 2007 Location: Scotland, Ayr www.amour weddingvideos.co.uk Posts: 305	Hi, having moved across from a sony camera I found the auto focus on the Canon to be slightly less responsive, however Auto focus should never really be trusted and the only way is to go manual. If you really cant go manual then zoom in tight on the subject, press the instant auto focus then release prior to re framing and that way you will know the subject is in focus. Hope this helps. john __________________ john estcourt www.amourweddingvideos.co.uk

January 23rd, 2010, 01:56 AM	#3
Chris Soucy Inner Circle Join Date: Feb 2007 Location: Fairfield, Dunedin, New Zealand Posts: 3,691 Images: 18	Hi Etienne........... There is no "strange behaviour" with the Canon auto focus, it's as good as the camerman behind it. Autofocus can only work if it has a discernible (to it) target to focus on. A small forground target with an immense background target makes for a poor autofocus scenario, especially if the former has no real contrast or outline. Dive into the menu's on the A1 and set grids to "ON": [Display Setup] - [Markers] - [Grid] If your target doesn't almost completely fill the box of the centre grid, IT WILL NOT FOCUS ON IT. Throw in bad contrast, poor lighting and a possibly dirty IAF sensor and you have a dogs dinner, where it will "do it's own thing" despite what you may think it should be doing. Do some tests and check it out and see for yourself how much of that centre box is required before the AF will consistantly lock to it, you'll be suprised (and no, it isn't any worse and actually a lot better than any other make of camera either). It's a poor workman who blames his tools for a bad job. CS